Pleiades, Merope, and Variability
Date: Summer 2012
My question is regarding the Pleiades described as the Seven Sisters in Greek Mythology. The loss of one of the sisters, Merope, in some myths may reflect an astronomical event wherein one of the stars disappeared from view by the naked eye. These 7 stars are a large part of many cultures around the world, not just Greece, but from Japan to India to the Mayan Civilization. I could not find anywhere what astronomical event may have caused one of the stars to not disappear (it is still there) but to no longer be visible to the naked eye. The Greeks give a very good myth describing this event so that means that it probably happened during their time and in astronomical terms that is VERY VERY recently (less than 2500 years ago). In the end, a simple way to put it my question is - could you please explain what is the actual event causing that star to fade.
While many scientists have speculated on the astronomical significance of the "lost Pleiad" of Greek Mythology, it might be too much to state that the myth of the lost sister as being driven by an actual astronomical event. There is very little independent evidence to support the idea that one of the stars in this cluster actually changed luminosity during the observation period we are talking about.
Certainly, there are natural variations to star luminosity. A main line star will evolve. However, since the stars of the Pleiades are blue-white stars, their evolutionary pattern does not support a decrease in luminosity over the time period we are talking about. There are other causes for stellar variability (planets passing in front of the star, natural star pulsation, etc.), but again, not so that the human eye might be certain to observe at the time scale of the event.
The Pleiades represents a cluster of stars that vary in visibility, from 2 or 3 to more than 7 depending on viewing conditions. So it is likely that the number seven was ascribed to this cluster because 7 is a sort of "magical" number (prime number that does not normally occur in nature). When we see something that could be 7 in nature, we tend to be drawn to it. I'm more inclined to think that ancient peoples looked up, saw a cluster of stars, saw that some nights some of these stars tend not to be visible, imagined "7" because 7 is rare in nature and has some mystical significance, built a story around this cluster.
Greg (Roberto Gregorius)
I think you may be right. It is certainly possible that one of the other stars faded during late Greek times. Which one is not known, but there are more than 500 stars visible through a telescope! Great question.
David H. Levy
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Update: December 2011